1. Field of the Invention
The present invention relates to a developer filling method for supplying developer to a developer cartridge used in such image forming devices as a printer, a photocopy machine, a facsimile device, or a multifunction device providing a combination of these functions; a developer cartridge; and a developer accommodating vessel.
2. Description of Related Art
Image forming device well known in the art including laser printers, photocopiers, facsimile devices, multifunction devices, and the like employ detachable developer cartridges for accommodating developer. These developer cartridges include a toner accommodating chamber for accommodating developer integrally formed with a developer roller for supplying the developer to a photosensitive drum in the image forming device. When the developer cartridge is mounted in the image forming device, a driving force from the image forming device is transferred to a developing roller to rotate the same, while developer is electrostatically attracted to the surface of the developing roller to form a thin layer thereon. This thin layer of developer is supplied to the photosensitive drum.
Powders, such as ground toner and polymer toner, are used as the developer. The particle size in the toner is approximately several to several tens of μm. When filling the developer cartridge with developer, the developer is dropped by gravity force from a hopper in a developer filling device into the developer cartridge. The operation needs to be done carefully so that the developer does not leak through a gap between the developer roller and a casing of the developer cartridge.
However when employing the method described above to fill the developer cartridge with developer, it is not possible to fill the developer cartridge with developer at a density greater than an apparent loose density, that is, the density of the developer compressed by its own weight. Hence, the volume of the developer cartridge must be greater than the volume of developer being introduced. This problem has been a detriment to attempts to reduce the size of the developer cartridge as well as the size of the image forming device.
On the other hand, one method for filling a vessel with toner is disclosed in Japanese patent application publication No. HEI-5-232810. This vessel includes an upper vessel cylinder having an open bottom end and a toner injection inlet formed in a suitable location, a lower vessel cylinder having an open top end, and a contracting cylinder for integrally coupling the lower edge on the open bottom end of the upper vessel cylinder with the upper edge on the open top end of the lower vessel cylinder in a watertight and airtight construction. The toner vessel includes at least one air escape through-hole at an appropriate location to allow air to escape when the contracting cylinder is contracted to compress the overall toner vessel. After filling the toner vessel with toner, the toner vessel can be compressed by moving the upper vessel cylinder toward the lower vessel cylinder to contract the contracting cylinder. In this way, the toner vessel can be made smaller, even when air enters the cylinder during the toner filling operation.
However, when filling the vessel with toner, the toner mixes with air when poured into the vessel into the vessel. Therefore, the vessel must be configured sufficiently long in the direction that the toner is introduced.
However, in the toner filling method disclosed in Japanese patent application publication No. HEI-5-232810, the direction for introducing toner is the same as the direction in which the toner vessel is compressed. In other words, the vessel is shortened in the filling direction. Therefore, by securing sufficient length of the vessel in the direction in which toner is introduced, the distance in which the vessel is compressed becomes longer, leading to various problems including a need to increase the length of the contracting cylinder, a need to increase the compressing distance, and an increased complexity in the filling operation.